This research program seeks to bridge the gap between the study of human brain processes which must utilize scalp-recorded electrophysiologic data, and the more detailed neurophysiologic analyses at the cellular level which can only be carried out in experimental animals, often under quite restricted conditions. Analyses of the scalp topography of potentials associated with sensory and motor processes in human subjects are compared with detailed surface and intracranial mapping of field potentials and cellular firing patterns in subhuman primates under similar experimental conditions. The latter studies provide direct information on the intracranial sources of surface-recorded potentials. Methods for estimating the intracranial sources of complex event-related potentials utilizing scalp topography are to be further developed and refined. The specific processes under investigation include cortical and subcortical responses to auditory stimuli, the neural activity associated with voluntary movement, and the cerebral processes associated with visual scanning. These investigations are intended to provide information on the sequences of cerebral neural activity which underlie these sensorimotor processes in man, as well as to provide a foundation for the effective use of scalp-recorded event-related potentials in clinical applications which requires information on the sources of these potentials.